To ensure the safety of carbon dioxide (CO) geological storage, it is important to effectively monitor the pore pressure, reservoir deformation and fluid plume migration, which poses new challenges to monitoring techniques and tools. In this paper, an innovative monitoring method is presented based on distributed fiber optic strain sensing (DFOSS) to detect the strain response distribution induced by fluid injection in real time. The original strain field distribution in the reservoir rock and the effect of the effective stress on the strain response were obtained for different confining and pore pressure combinations. Then, the rock strain during displacement was measured to dynamically monitor the movement front of the wetting phase. The results showed that the core strain response curves under the influence of the confining and pore pressures exhibit significant edge effects, with lower strain values in the vicinity of the artificial confinement facility than in the reservoir. In addition, the overall strain response exhibited an increase corresponding to the increase in the confining pressure. A higher confining pressure was observed to mitigate the pore pressure expansion-related strain in the rock itself. This proves that the selection of a large-depth subsurface reservoir could help to increase the CO injection pressure and rate, and the formation pressure threshold value identified in this study varied between 6 to8 MPa. Furthermore, the full-field strain history showed that fiber optic technology can be employed to accurately monitor the detailed characteristics of front movement and core deformation during wetting fluid displacement, including the history of the strain distribution due to two-phase motion and the change in the two-phase moving speed. The analysis results collectively validated the applicability of this monitoring technique for core-scale testing. The data and conclusions obtained could contribute to a deeper comprehension of the DFOSS reservoir monitoring capability. Furthermore, these findings hold relevance for subsequent experimental analyses, numerical simulations, and field applications at carbon capture and storage sites.

中文翻译：

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通过分布式光纤应变传感监测二氧化碳储存库中的流体运移：实验室研究

为了确保二氧化碳地质封存的安全，有效监测孔隙压力、储层变形和流体羽流运移具有重要意义，这对监测技术和工具提出了新的挑战。本文提出了一种基于分布式光纤应变传感（DFOSS）的创新监测方法，用于实时检测流体注入引起的应变响应分布。获得了不同围压和孔隙压力组合下储层岩石中的原始应变场分布以及有效应力对应变响应的影响。然后，测量位移过程中的岩石应变，以动态监测润湿阶段的运动前沿。结果表明，围压和孔隙压力影响下的岩心应变响应曲线表现出明显的边缘效应，人工围困设施附近的应变值低于储层内的应变值。此外，总体应变响应随着围压的增加而增加。观察到较高的围压可以减轻岩石本身与孔隙压力膨胀相关的应变。这证明选择大深度地下储层有助于提高CO注入压力和速率，本研究确定的地层压力阈值在6~8 MPa之间变化。此外，全场应变历史表明，光纤技术可以准确监测润湿流体驱替过程中前沿运动和岩心变形的详细特征，包括两相运动引起的应变分布历史和两相移动速度。分析结果共同验证了该监测技术对于核心规模测试的适用性。获得的数据和结论有助于更深入地了解 DFOSS 水库监测能力。此外，这些发现对于后续的实验分析、数值模拟以及碳捕获和储存地点的现场应用具有相关性。